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      <title>什么是 Nginx 的缓存？如何设置？ - 交互式测验</title>
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    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>什么是 Nginx 的缓存？如何设置？ - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
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                      <p id="question-text"></p>
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      </div>

      <script>
        const quizData = [
  {
    "question": "根据文档，Nginx的FastCGI缓存（FastCGI Caching）主要用于什么目的？",
    "options": [
      "缓存静态资源，如HTML文件、CSS和图像",
      "当Nginx作为反向代理时，缓存从后端服务器获取的响应数据",
      "缓存通过FastCGI协议处理的动态内容，例如PHP脚本生成的页面",
      "在高并发场景下使用极短时间的缓存策略来提升性能"
    ],
    "correctAnswerIndex": 2,
    "explanation": "FastCGI缓存专门用于缓存通过FastCGI协议与应用服务器（如PHP-FPM）通信后生成的动态内容。这可以极大地减少重复执行脚本的开销，从而提高动态页面的响应速度。",
    "source": "文档中「Nginx 缓存的基本概念」->「缓存类型」部分",
    "hint": "文档中提到了几种不同的缓存类型，思考一下FastCGI协议通常与哪类内容相关？"
  },
  {
    "question": "在Nginx缓存配置指令 `proxy_cache_path /path/to/cache levels=1:2 keys_zone=my_cache:10m max_size=1g;` 中，`keys_zone=my_cache:10m` 参数的作用是什么？",
    "options": [
      "设置缓存目录在磁盘上的总大小为10MB",
      "定义一个名为my_cache、大小为10MB的共享内存区域，用于存储缓存键和元数据",
      "指定缓存的Zone（区域），以便进行安全隔离",
      "限制单个缓存文件的最大尺寸为10MB"
    ],
    "correctAnswerIndex": 1,
    "explanation": "`keys_zone` 参数用于定义一个共享内存区域，它不存储实际的缓存文件内容，而是存储缓存的索引信息，即缓存键（cache keys）和相关的元数据（metadata）。这使得Nginx可以快速查找一个请求是否存在缓存，而无需扫描磁盘文件。",
    "source": "文档中「Nginx 缓存的配置基础」->「1. 缓存目录设置」部分",
    "hint": "这个参数的名字`keys_zone`暗示了它的用途。它不是用来存储文件内容的，而是用来存储“钥匙”（keys）的。"
  },
  {
    "question": "Nginx的 `proxy_cache_use_stale` 指令在什么场景下特别有用？",
    "options": [
      "当管理员需要手动强制刷新所有缓存时",
      "当客户端请求头明确要求不使用缓存时",
      "当后端源服务器发生错误、超时或无法访问时",
      "当缓存目录的磁盘空间已满时"
    ],
    "correctAnswerIndex": 2,
    "explanation": "`proxy_cache_use_stale` 指令允许Nginx在后端服务器出现问题（如返回5xx错误、超时等）的情况下，使用一份已经过期的（stale）缓存来响应客户端请求。这是一种提升服务容错性和高可用性的重要机制，可以避免将后端错误直接暴露给用户。",
    "source": "文档中「Nginx 缓存的配置基础」->「2. 缓存区块设置」部分",
    "hint": "考虑一下“stale”（不新鲜的，过期的）这个词的含义。在什么情况下，即使内容过期了，提供它也比不提供要好？"
  },
  {
    "question": "当Nginx收到一个请求时，它如何判断这个请求是否在缓存中已存在（即缓存命中）？",
    "options": [
      "通过检查客户端的IP地址",
      "通过比较请求的HTTP方法（GET/POST）",
      "通过将请求URI、参数等信息生成一个唯一的缓存键（Cache Key），并在缓存存储中查找该键",
      "通过检查响应头中的`Set-Cookie`字段"
    ],
    "correctAnswerIndex": 2,
    "explanation": "Nginx通过一个称为“缓存键”（Cache Key）的唯一标识符来管理缓存。它会根据请求的URL、参数以及配置中定义的其他变量来生成这个键。然后，Nginx使用这个键的哈希值在缓存目录中快速查找对应的缓存文件，从而判断是缓存命中还是未命中。",
    "source": "文档中「Nginx 缓存的工作原理」->「1. 缓存请求的处理」->「缓存键的生成」部分",
    "hint": "文档提到，每个缓存的数据都需要一个“唯一标识”。这个标识符是如何生成的？"
  },
  {
    "question": "为了防止在高并发下，当一个缓存项失效时，大量相同请求同时“穿透”到后端服务器，应该使用哪个Nginx指令？",
    "options": [
      "proxy_cache_bypass",
      "proxy_cache_revalidate",
      "proxy_cache_lock",
      "proxy_cache_min_uses"
    ],
    "correctAnswerIndex": 2,
    "explanation": "`proxy_cache_lock` 指令是解决“缓存惊群”问题的关键。当多个客户端同时请求一个不存在的缓存项时，该指令会只允许第一个请求到达后端服务器去获取数据，而其他相同请求则会等待第一个请求完成并填充缓存。这样可以有效避免后端服务器的瞬时压力过大。",
    "source": "文档中「Nginx 缓存的高级配置」->「4. 缓存同步与一致性」部分",
    "hint": "在高并发场景下，如何避免多个请求同时去“重建”同一个缓存？文档提到了一个“锁”机制。"
  },
  {
    "question": "根据文档内容，以下哪项不是Nginx缓存清理与失效的策略之一？",
    "options": [
      "时间驱动的失效（根据过期时间自动清理）",
      "容量限制清理（达到最大容量时清理旧数据）",
      "LRU（Least Recently Used）策略（清理最不常访问的数据）",
      "FIFO（First-In, First-Out）策略（按存入顺序清理最早的数据）"
    ],
    "correctAnswerIndex": 3,
    "explanation": "文档中明确提到了三种缓存清理策略：基于时间的失效（`inactive`参数）、基于容量的清理（`max_size`参数）以及LRU（最近最少使用）策略。虽然FIFO是一种常见的缓存淘汰算法，但在本文档中并未提及它是Nginx使用的策略。",
    "source": "文档中「Nginx 缓存的工作原理」->「4. 缓存清理与失效策略」部分",
    "hint": "仔细阅读文档中关于“缓存清理与失效策略”的列表，看看哪一个常见的缓存算法没有被提及。"
  },
  {
    "question": "如果希望手动、按需地清除Nginx缓存中的特定URL内容，应该使用哪个指令来实现？",
    "options": [
      "proxy_cache_valid",
      "proxy_cache_purge",
      "proxy_cache_key",
      "proxy_no_cache"
    ],
    "correctAnswerIndex": 1,
    "explanation": "`proxy_cache_purge` 指令专门用于实现缓存清理功能。通过配置一个特定的location（例如 `/purge`），并向该location发送请求，可以精确地清除与指定缓存键匹配的缓存项。这对于内容更新后需要立即刷新缓存的场景非常有用。",
    "source": "文档中「Nginx 缓存的高级配置」->「5. 缓存的热更新与清理」部分",
    "hint": "文档中有一个专门的配置示例，展示了如何设置一个 `/purge` 路径来清理缓存。这个功能是靠哪个指令实现的？"
  }
];
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        let score = 0;
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            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  